A grain-harvesting combine includes a header, which cuts the crop and feeds it into a threshing rotor. The threshing rotor rotates within a perforated housing, performing a threshing operation of the grain from the crop directed thereinto. Once the grain is threshed it falls through perforations in the housing onto a grain pan. From the grain pan the grain falls through a set of upper and lower sieves that are known as a cleaning shoe. The sieves are vibrating or oscillating, causing clean grain to fall through for the purposes of collection. A cleaning fan blows air through the sieves, discharging chaff toward the rear of the combine. Crop residue such as straw from the threshing section proceeds through a straw chopper and out the rear of the combine.
In a combine some of the chaff and straw is mixed with grain after the threshing operation. The cleaning assembly removes these contaminants from the grain. In most harvesting machines the cleaning assembly includes the blower, an upper sieve and a lower sieve. The blower has its own housing, whereas the upper sieve and lower sieve are part of a cleaning shoe.
What is needed in the art is an efficient and effective way of controlling the cleaning shoe and cleaning fan speeds.